对象数组：想要访问一个属性但我得到“试图获取非对象的属性...”

From my database I get only one result. Nevertheless I get an array returned because of this code

while($obj = $stmt->fetch(PDO::FETCH_OBJ)){
    $result[] = $obj;
}

The returned array has only one element (object) at the index 0. From this object I want access a property.

My code looks like:

return $result[0]->_id;

I get the notice

Trying to get property of non-object in ...

Here are my dumps:

var_dump

array(1) { [0]=> object(stdClass)#4 (13) { ["_id"]=> string(8) "43001613" ["another-property"]=> string(5) "20608" } }

print_r

Array
(
    [0] => stdClass Object
        (
            [_id] => 43001613
            [another-property] => 20608
        )

)

It is for sure only a small error but I can't figure it out now.

Edit: Here is the full function:

public function getOrtIDForPLZ($plz){
    $sql = "SELECT * FROM verortung WHERE plz = :plz LIMIT 1;";
    $result = $this->ExecuteQuery($sql, array("plz"=>$plz));

    var_dump($result);
    echo '<pre>';
    print_r($result);
    echo '</pre>';

    return $result[0]->_id;
}

Output:

array(1) { [0]=> object(stdClass)#32 (13) { ["_id"]=> string(8) "43006637" ["gemeindekennziffer"]=> string(5) "32330" ["gemeindename"]=> string(13) "Theresienfeld" ["ortsname"]=> string(13) "Theresienfeld" ["plz"]=> string(4) "2604" ["bezirk"]=> string(21) "Wiener Neustadt -Land" ["bundesland"]=> string(17) "Niederösterreich" ["lat"]=> string(11) "47.85000000" ["lon"]=> string(11) "16.23333330" ["einwohner_2001"]=> string(4) "2490" ["kfz-kennzeichen"]=> string(2) "WB" ["fläche_km2"]=> string(5) "11.44" ["seehöhe"]=> string(3) "282" } }

Array
(
    [0] => stdClass Object
        (
            [_id] => 43006637
            [gemeindekennziffer] => 32330
            [gemeindename] => Theresienfeld
            [ortsname] => Theresienfeld
            [plz] => 2604
            [bezirk] => Wiener Neustadt -Land
            [bundesland] => Niederösterreich
            [lat] => 47.85000000
            [lon] => 16.23333330
            [einwohner_2001] => 2490
            [kfz-kennzeichen] => WB
            [fläche_km2] => 11.44
            [seehöhe] => 282
        )

)

NULL

Notice: Trying to get property of non-object in /home/www/home/includes/class.DatabaseQuery.php on line 4507

You're probably calling this method multiple times. In the first call everything is all right, but in the next one...

See that NULL? Surely you cannot get a property of NULL.

If that's not the case, then line 4507 points to somewhere else.